(Paths will have to be adjusted for your environment (and if you're on linux you will of course have to use a shell script instead, but the content wont differ much. Then the printer will just have to "print double sided")

Other example for 32 pages on A3 sheets :
(Paths will have to be adjusted for your environment (and if you're on linux you will of course have to use a shell script instead, but the content wont differ much. Then the printer will just have to "print double sided")

Adobe Reader 8 and 9 will do booklet printing for you. For a A4 booklet, you just need to export an A5 document to PDF and then tell Adobe Reader to print it as a booklet. With Reader 9 you do not have to prepare a certain size as the Reader can scale (not sure if any precision issues). Depending on needs you may want the "Multiple Pages Per Sheet" or the "Booklet Printing" option in the Print Dialog "page scaling" option drop down.

PDFSaM is a very reliable Java-based tool that provides many options to manipulate PDF files. Especially recommended for pre-press work!

jPDF Tweak is a versatile Java-based tool with loads of options to edit PDF files.

Comment on these tools (20/06/2010) :
- Multivalent req'es outdated Java 1.4 to be installed. Trying to run with a current JRE is running into "java.lang.ClassNotFoundException: tool.pdf.Impose" error.
- PoDoFo (on-line) appears to be unaccessible
- PDFSaM is a well-done collection of PDF-tools, but lacks imposition features (in particular like n-up printing)
- jPDF Tweak is a bit tricky to use, but appears to be most functional (and, by now, stable). Did not find a settings export or batch function though.